In 1992, Susan Cummings was a 47-year-old, struggling actress in New York City when she was diagnosed with early- stage breast cancer. The story that Cummings, now of Bernardston, tells in her new book, “Adventures of a One-Breasted Woman: Reclaiming My Moxie After Cancer,” begins in a medical center where she has just had a mammogram. The technician peeks in …